Enhanced photogeneration of polaron pairs in neat semicrystalline donor-acceptor copolymer films via direct excitation of interchain aggregates

Daniele Di Nuzzo, Daniele Viola, Florian S.U. Fischer, Giulio Cerullo, Sabine Ludwigs, Enrico Da Como

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

We investigate the photogeneration of polaron pairs (PPs) in neat films of the semicrystalline donor-acceptor semiconducting copolymer PCPDTBT. Carefully selecting the solution-processing procedures, we obtain films with different amounts of crystallinity and interchain aggregation. We compare the photogeneration of PPs between the films by monitoring their photoinduced absorption in ultrafast pump-probe experiments, selectively exciting nonaggregated or aggregated polymer chains. The direct photoexcitation of interchain π-aggregates results in prompt (<100 fs) charge generation. Compared to the case where nonaggregated chains are excited, we find an 8-fold increase in the prompt PP to singlet-exciton ratio. We also show that highly crystalline lamellar nanostructures not containing π-stacked or any light-absorbing aggregates do not improve the efficiency of PP photogeneration. Our results show that light absorption from interchain aggregates is highly beneficial for charge photogeneration in semiconducting polymers and should be taken into account when optimizing film morphologies for photovoltaic devices.

Original languageEnglish
Pages (from-to)1196-1203
Number of pages8
JournalJournal of Physical Chemistry Letters
Volume6
Issue number7
Early online date19 Mar 2015
DOIs
Publication statusPublished - 2 Apr 2015

Keywords

  • charge generation
  • nanomorphology
  • organic electronics
  • organic photovoltaics
  • ultrafast optical spectroscopy

ASJC Scopus subject areas

  • Materials Science(all)
  • Physical and Theoretical Chemistry

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